VIDEO: This animated TRMM Multisatellite Precipitation Analysis shows the rainfall that occurred with Tropical Cyclone Mahasen during the week of May 6 through 13, 2013 as it moved through the Bay...
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Credit: Credit: Hal Pierce, SSAI/NASA Goddard

Tropical Cyclone Mahasen has been strengthening and expanding as it moves through the northern Bay of Bengal for a landfall on Thursday, May 16. NASA's Aqua satellite passed over the cyclone as it was hugging the central India coastline. Rainfall data from NASA's TRMM satellite was compiled in an animation to reveal large rainfall totals as the storm tracked through the Bay of Bengal earlier this week.

Mahasen is being pushed to the northeast by a trough (elongated area) of low pressure and is expected to make landfall in Bangladesh. BBC News reported on May 15 that an evacuation is under way for hundreds of thousands of residents in coastal areas of Bangladesh. The cyclone is expected to affect low-lying areas of Burma's Rakhine state, where tens of thousands reside in camps.

Although Mahasen is not a strong cyclone, it is large and will generate a storm surge over a large area along the coastline. The storm surge poses the greatest danger to residents of Bangladesh.

NASA's Aqua satellite passed over Cyclone Mahasen on May 15 at 07:45 UTC (3:45 a.m. EDT) and the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument captured a visible image of the storm. The MODIS image showed that the storm has expanded over the last several days. In the MODIS image, strong, high thunderstorms are visible north and northeast of the center, as they cast shadows on surrounding storms that make up the cyclone. NASA's Tropical Rainfall Measuring Mission (TRMM) multisatellite Precipitation Analysis was animated at NASA's Goddard Space Flight Center in Greenbelt, Md. to show the rainfall that occurred with Tropical Cyclone Mahasen during the week of May 6 through 13, 2013. The animation depicted Mahasen as it moved through the Bay of Bengal. The bulk of Mahasen's rain had fallen mainly over the open waters of the northern Indian Ocean and the Bay of Bengal during that period. The TRMM analysis showed that rainfall totals of about 500 mm (~19.7 inches) fell west of Indonesia in this analysis.

On May 15 at 0900 UTC (5 a.m. EDT), Cyclone Mahasen's maximum sustained winds were near 45 knots (51.7 mph/83.3 kph). Mahasen's center was located near 17.9 north latitude and 88.2 east longitude, about 308 nautical miles (354 miles/570 km) south of Kolkata, India. Mahasen is tracking to the north-northeast at 12 knots (13.8 kph/22.2 kph).

The exact location of landfall is still uncertain, but using three different computer models, forecasters interpolate between them and have an idea of the general area where Mahasen will hit the coast. The American GFS computer model takes Mahasen the farthest west, the Indian Met Service model brings Mahasen further south, and the U.K. Met Service model takes it even further south, so forecasters are interpolating the storm's track.

Warnings are already in effect for Bangladesh. As of 9:51 a.m. EDT (13:51 UTC) on May 15, the Bangladesh Meteorological Department (BMD) issued Danger Signal Number 7 for Chittagong and Cox's Bazar and Danger Signal Number 5 for Mongla. Because Mahasen is expected to bring very heavy rainfall, the BMD warns that in addition to flooding, landslides are possible in the elevated regions of the Chittagong division. For specifics on the effects for the Danger Signal areas, go to: http://www.bmd.gov.bd/Content.php?MenuId=41&SubMenuId=59.

All ocean vessels in North Bay have been warned to remain in port or find shelter until further notice. For updates from the Bangladesh Meteorological Department, visit: http://www.bmd.gov.bd/.

Regardless of where exactly the center comes ashore this is a large cyclone. As a result of its size it is expected to bring a large storm surge above 2 meters, according to the Bangladesh Meteorological Department. So many live a few meters above sea level, which makes them more subject to flooding.

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